Adjusting insulin pump dosages with exercise: recent udpates
by Adam Burrack, PhD
Ever wonder what the “best practice” for adjusting insulin dosages around the time of exercise is? Well, you’re in luck! In a recent study, a group of French researchers tested whether decreases in bolus (meal-time) or basal rate (BR) insulin are more effective in preventing low blood sugars during and immediately following moderate intensity aerobic exercise. The researchers picked a logistically important time point: three hours following the most recent meal. As many diabetic athletes know, exercising either first thing in the morning or in the late evening are generally our best options for “fitting in” our daily workouts. Pre-breakfast workouts represent perhaps the easiest insulin dose adjustment – usually none – but many athletes prefer higher-end aerobic work in the evenings or on weekend afternoons. As such, this 3-hour post-meal time point was worth investigating.
This particular research group has been studying the interface of insulin pump adjustment algorithms and exercise for a number of years. In a 2009 manuscript these authors investigated whether combination management system called Flexible Intensive Insulin Therapy (FIT) would improve blood sugar level control. Even though insulin doses for individuals did not change much for specific situations over this 4-month study, the digital real-time data collection and archiving appeared to facilitate patient’s learning their own patterns. This self-knowledge allowed further customization of diabetes management, guided by physicians.
A 2012 study from this group in the journal Diabetes and Metabolism investigated simple algorithms to adjust for physical activity based on intensity of the exercise session. Algorithms for insulin dose adjustments aimed to reduce the insulin dose of the meal preceding exercise by 30% and 50% for moderate and intense exercise, respectively. In addition, a 50% reduction with extra carbohydrates was proposed for intense exercise of abnormally long duration. These algorithms were entered into the Diabeo system and subjects were monitored for 4 months. Sanofi, which is based in France, was the commercial source of the Diabeo platform used in this study. Results were encouraging. Participants experienced less frequent and less severe post-meal low BG and less frequent high BG events following exercise and the above insulin dose requirements.
On a personal note, these types of “short cuts” for insulin dosing are very similar to what I empirically reached shortly after I started insulin pump therapy, when I was training for and racing cross country and track at UW-Stout in the early 2000s (2002 to 2004). At that time I was using a 25% reduction of next-meal bolus – in consultation with my medical team at the time – following high-intensity running workouts. Since we had practice starting at 3pm (fall cross country) or 4pm (winter or spring track) at that time, and my lunch meal was generally noon or 12:30pm (and I was often sedentary between lunch and practice, often in a biology, chemistry, or physics laboratory course session), I did not need to pre-adjust my carbohydrate bolus down at that time. Interestingly, as I’ve aged and my basal rates have crept upward, this adjustment has remained useful for my next-meal bolus following hard interval running or cycling workouts.
An important note on determining your own exercise-induced insulin adjustments: don’t use mine as a guide. Discuss and adjust with your own medical team and figure out what works for you. Response to injected insulin is highly individual and depends on aerobic condition, exercise intensity, and other individual factors including hormone levels, quantity/quality of sleep, and other stressors. Diabetes management is empirical, but consult with your medical team before implementing any changes. Multiple perspectives from medical professionals can be very helpful in making these types of diabetes management decisions.
In a more recent study in Diabetes and Metabolism, authors from this group studied whether the application of a combination of smart phone and phone apps could improve HbA1c as a longer-term measure of overall T1D management. Encouragingly, yes these tools do appear to have potential as adjuncts to T1D care. This study is continuously recruiting patients with either T1D or T2D to participate in a larger-scale evaluation of whether the Diabeo system can improve diabetes management. While these technological improvements are neat, I am often struck by the thought that the technology improves our management of T1D, while understanding the biology of the disease and how the immune system works is where a cure for T1D will come from. Having said that, the above types of insulin dose adjustments and insulin pump improvements help individuals with T1D live healthier lives while immunologists like those I have profiled in our series continue to work on cure-focused basic research in the background ☺
YouGlycemia: Active Diabetes Management